A pair of volumes "Locomotives" by A.Morton Bell, sixth edition published 1948.
I have a set of these of my own and rate them highly for the breadth and depth of coverage and clear description of the technical nitty-gritty of the steam locomotive. If you don't know your flexible stays from your droplinks, they're worth having on the shelf! Hardbacked in maroon cloth with gilt titles, some marking inside front covers but generally in good condition at nearly 60 years old, no loose pages, profusely illustrated, foldout plates intact.
Volume 1, 223pp
General description
The boiler
Superheating
Cylinders and valves
Framing and wheels
Lubrication
Tenders
Continous brakes
Feed-water
Volume 2, 451pp
Repairs
Maintenance
Combustion and fuel
Running faults and failures
Shop arrangements
The enginemen
Electric locomotives
Diesel locomotives
Special types of locomotives
Modern types of locomotives
4-6-2 express
LMS Royal Scot
LMS 4-6-0 5XP
LMS 4-6-0 Baby Scot
LMS 2-6-4T
LMS 2-8-0 Freight
LMS Standard 0-6-0
LMS Steamlined 4-6-2
LNER 2-6-0 mixed traffic
LNER 4-6-0 mixed traffic
LNER 2-6-0 mixed traffic
GWR 4-6-0 Castle class
GWR 2-8-0 freight
etc.